The present invention relates to an antenna coupler for switching digitally weighted values of inductance and or capacitance into and out of the circuit between an antenna and a utilization circuit such as a radio transmitter. More particularly, the present invention is related to an antenna coupler in which the switching is accomplished by the application of an electrical potential to control the bias of one or more diodes associated with the element being switched.
Antenna couplers are well known in which inductive and capacitive elements are selectively switched into and out of the circuit. Vacuum relays are typically used but are generally unsatisfactory as a result of their slow switching speed and operating life.
The use of PIN diodes as switching elements is also well known. For example, diodes are used in the operation of a transmit/receive or T/R switch which selectively couples the antenna to either a transmitter or receiver.
However, isolation is generally a problem in the use of PIN diodes for switching RF circuit elements in that the RF energy present in the antenna circuit would otherwise destructively overload the drive circuits for the PIN diodes. While inductors have been used for isolation purposes, the use of such inductors in close physical proximity to the antenna generally results in an unacceptable degradation of the antenna coupler.
It is accordingly an object of the present invention to provide a novel antenna coupler and method using PIN diodes as the switching elements.
Another object of the present invention is to provide a novel antenna coupler and method in which inductive isolation for the driver circuits for the switches does not unacceptably degrade the antenna coupler.
Still another object of the present invention is to provide a novel switchable inductive element and method of forming.
Yet another object of the present invention is to provide a novel autotransformer and method of forming.
These and many other objects and advantages of the present invention will be readily apparent to one skilled in the RF antenna art from the claims and from the following detailed description when read in conjunction with the appended drawings.